This invention was developed specifically for the correction of Wobbler syndrome in horses, which is a form of progressive ataxia due to instability of the cervical spine creating encroachment on the spinal cord (equine cervical vertebral malformation). Earlier attempts by the inventor to surgically stabilize the spine in horses utilized placement of a precut bone dowel within a prepared hole centered over the disk and partially cut into the vertebral end plates both above and below the disk. A discussion of these attempts was published in the 1979 Spring Issue of the Spokane County Medical Society Bulletin.
One difficulty posed by this earlier work related to the inherent biological problems in using allografts (tissues transplanted between individuals that are members of the same species but are not genetically identical) or xenografts (tissues transferred between different species). While the fusion technique using dowels has been successfully applied to humans by using bone taken from a remote area of the body, this is impractical when the technique is applied to horses. Removal of bone from the leg of a horse, as an example, would seriously affect the running ability of the horse. In addition, in all applications, dowels produced as autografts (tissues transplanted from one site to another site in the same individual) involve two separate surgical operations, with resulting increases in the likelihood of complications.
It is well known that autogenous tissues are considered to be the most biologically suitable graft material. Histocompatibility differences between donor and recipient do not exist, and there is no possibility of transmitting disease from one individual to another. The potential disadvantages of autografts include the need to sacrifice normal structures elsewhere in the body, morbidity associated with a second surgical site or extended primary incision, and limitations in the size, shape, and quality of available autogenous tissues.
The instant method of bone-to-bone fusion not only immediately stabilizes the joint, as does the dowel technique when successful, but also promotes bone growth across the joint by use of readily available autogenous tissue in the form of bone fragments removed during preparation of the joint. No additional surgery or bone removal is required. This invention further answers the need for perfect cylindrical bone dowels implant, which are impossible to meet when using natural bone.